The Archeology—Bone Bed I

This scene shows an artist's conception
of Ice-Age bison near a waterhole somewhere out on the grassy
and wind-swept southern Plains. Drawing by Hal Story, courtesy
Texas Memorial Museum.

A small group of camels graze on grasses.
Drawing by Hal Story, courtesy Texas Memorial Museum.

The modern bison on the left is considerably
smaller than the Bison antiquus shown on the right. Drawing
by Hal Story, courtesy Texas Memorial Museum.

Skull of short-faced bear found at Freisenhahn
Cave near San Antonio. Drawing by Hal Story, courtesy Texas
Memorial Museum.

The deepest and oldest layers in Bonfire Shelter containing
animal bones are known collectively as Bone Bed 1 and are present
only in the central part of the shelter. Together the Bone Bed 1
layers are 20-24 inches (50-60 cm) thick and begin directly below
Bone Bed 2 at a depth of 6.5 ft (2.2 m) below the shelter's modern
surface). There is only a single radiocarbon date from Bone Bed
1, and it establishes a minimum age of 11,500 B.C. Most likely Bone
Bed 1 is several thousand years older. Several facts about Bone
Bed 1 are remarkable.

Almost all of the identified bones are from
extinct animal species.

These include wooly (Mammuthus sp.), camel (Camelops
hesternus), at least one species of horse (Equus francisci), a small
antelope (Capromeryx sp.), and bison (Bison antiquus or occidentalis).
All of these animals disappeared from Earth at the end of the last
Ice Age (the Pleistocene) before 9,000 B.C. Although it is unlikely
that humans alone were responsible for the Late Pleistocene extinctions
in North America, they almost certainly contributed to the wave
of extinctions brought on by major climatic changes.

Drawings of many of the Ice-Age animals whose bones
were found in Bone Bed 1 at Bonfire help us visualize the environment
that early human groups in the region would have encountered. The
bison, Ice-Age and modern, that were killed at Bonfire probably
spent most of their lives on the southern Plains to the north.

Only one bone found in the uppermost layer of Bone
Bed 1 is of a species that survives today, the gray fox (Urocyon
cinereoargenteus). The species list given here does not include
any of the small animals (rats and such) present in the sediment
samples collected as microfauna samples; these have yet to be fully
analyzed.

Bone Bed 1 consists of at least five bone-bearing
layers.

Of the five bone-bearing layers now known (Strata
D, E, H-1, H-2, and I), several are very thin and do not extend
across the entire excavated area in the center of the shelter. It
is likely that if the excavation area is ever expanded in the future,
other minor layers will be found within Bonfire's lower deposits.
Stratum D contains only the gray fox bone and Stratum H-2, only
three antelope bones. The other three layers have multiple species
and are considered by Bement to represent separate bone beds. These
are discussed below.

The bones were introduced into the shelter by
predators, but not necessarily humans.

By the time Bone Bed 1 began forming, perhaps between
12,000-14,000 B.C., the floor of Bonfire Shelter was already high
and dry above the down-cutting canyon floor (although probably not
by much). Lacking any evidence of stream deposits that might have
washed bones into the shelter, there is no other credible alternative
to explain the presence of splintered and broken bones from a variety
of animals, many quite large. Predators carried or dragged dead
animals or body parts into the shelter or else they trapped animals
in the cave and killed them there. But which predators? The most
likely candidates include humans and three now-extinct carnivores:
the short-faced bear (Arctodus simus), a sabertoothed cat known
as scimitar cat (Homotherium serum), and wolf, possibly the dire
wolf (Canus dirus) or gray wolf (Canus lupins). Although lacking
definite proof such as the presence of stone tools or hearths, the
Bonfire investigators have argued that humans were the chief Bone
Bed 1 predator. See
Who were the Bone Bed 1 Predators? for a summary of the arguments
and evidence.

Bone Bed 1, unlike the later bone beds, did
not form as the result of "jumps."

The jump explanation can be rejected for two reasons.
One is that Bone Bed 1 is concentrated in the central, interior
part of Bonfire Shelter and is not present at the south end adjacent
to the talus cone where both of the upper bone beds are concentrated.
Secondly, there are multiple species present in Bone Bed 1 including
species that are poor candidates for having been driven over cliffs.
Mammoths were extremely large creatures that, based on what is known
about their modern elephant cousins, were highly intelligent and
wary. They lived in smaller social groups (families) and were not
as prone to bolt and run pell-mell as bison. Camels, horses, and
antelope are all fleet-footed animals that should have been able
to evade small groups of hunters upon the rolling grassy plains
that probably covered the uplands above Bonfire Shelter in the Late
Pleistocene. There is no definitive evidence that any of these species
were killed by the jump method anywhere in North America. See Who
were the Bone Bed 1 Predators? for an alternative explanation.

The Bone Bed 1 Layers

Three of the layers in Bone Bed 1 (Stratum E, H-1,
and I) could and probably should be considered as separate bone
accumulations (i.e., bone beds) on their own merits. All three probably
formed in a relatively short time and contained numerous large bones
of at least two different creatures. All three also had what Bement
believes is a highly significant pattern: the presence of limestone
blocks lying in association with splintered and broken long bones.

Stratum E Bone Bed

Stratum E contained the remains of at least three
horses (mostly juveniles), a camel, a bison, and a mammoth. Bones
from all four species were found close together and in apparent
association with one large limestone block (somewhat larger than
a basketball) and several smaller ones. Most of these bones were
hind- and front-leg bones of horse, bison, and camel. Not far away
were several other clusters of smaller limestone blocks and splintered
bone.

Stratum H-1 Bone Bed

Stratum H-1 contained bones from at least two horses
and a young mammoth. The horse bones were by far the most numerous.
One horse was a mature adult (at least 3.5 years old) and one was
a colt, less than a year old, based on dental eruption patterns
and fusing of certain bones. The range of bone elements present,
leg and feet bones, skull and teeth fragments, and various vertebrae,
suggest that the entire carcass was once in the shelter. The mammoth
was less well represented, but the presence of mandible fragments,
a vertebra, and fragments of the pelvis, tibia (upper front leg),
and a rib, suggests that much of the animal was in the shelter.
Once again there were several clusters of limestone blocks and broken
bones. The most impressive was a line of five limestone rocks, two
of which were directly associated with fragmented horse bones including
the ends of two ulnas (lower front legs) and one sacrum (tail bone)
broken along its center line.

Stratum I Bone Bed

This layer contained bones from a large bison and
the teeth from at least one adult horse. The bison was represented
by a variety of post-cranial (everything below the head) elements
including vertebra, leg bones, foot bones, ribs, shoulder, and pelvis.
Three large boulders dominated the bone bed, but these rested on
lower layers and thus pre-date Stratum I. Seven smaller but still
hefty limestone blocks were found amid fractured bison bones. In
another area of the deposit, a separate limestone block was found
alongside more fragmented bison bones and several horse teeth.

Mammoth and horse bones in place in Bone
Bed 1, Stratum E (upper bones) and Stratum H (lower bons).
Photo taken in 1984 by Herb Eling..

Click images to enlarge

Wooly mammoths, such as the one shown here,
would browse the lower limbs of their favored tree species
causing them to have a trimmed-up look, much as modern elephants
do today. Drawing by Hal Story, courtesy Texas Memorial Museum.

A stallion senses trouble (note the crouching
hunters in the distance) and moves to protect his mare and
her colt. Some of the Ice-Age horse bones from Bonfire are
virtually identical to those of modern horses. Drawing by
Hal Story, courtesy Texas Memorial Museum .